I would say it is only half right. Of course, most best communicators in the world are met among politics managers, as being able to correctly express themselves is an essential skill for them to hold their position. Still, we see loads of examples, when politics cannot organize their speech in a proper logical way and managers cannot find a proper way to communicate with people they are working with. Having any kind of power can be dreadful for each person. We are creatures fulfilled with egoism, so the more power we have, the more is the seduce to use for your own purposes or to show off with it simply. It is not a rule, of course, but this fact is one of the most frequent reasons to spoil communication skills or completely ‘remove the necessity’ of being an excellent communicator when you are a boss.